Skip to main content

Full text of "The Cambridge Natural History"

See other formats


346              TOOTH GERMS IN WHALEBONE WHALES            CHAP.

driven upwards by the forcible expulsion of air from the lungs.
But for the most part the water which is spouted is simply
condensed breath.

like some, but not all, other aquatic Mammalia the Whales
have apparently no external ear. Indeed the opening of the ear
is excessively small. In a huge Rorqual it will " admit a quillw;
aad although " a quill" is rather vague, we may fairly allow any
sized quill without proving that the orifice of the auditory
passage is anything but exceedingly minute. As a proof, added
to so many, that the Whales are the progeny of terrestrial creatures,
we have the occasional traces of external ears.1

FIQ. 182,—Left lower jaw of foetus of Bala&noptera rosfrata.    Inner aspect,
natural sizes showing teeth.    (After Julin.)
Whalebone Whales never possess permanent teeth as well as
the baleen; but in the foetus are more than traces of true teeth,
which, however, never arrive at maturity. The whalebone itself is
described later (p. 3 5 4). That the Whalebone Whales possess teeth
while in the foetal condition was discovered so long ago as 1807.
It has since been confirmed by many observers. Not only is there
one set of teeth developed in the foetal Salaenoptera but two,
of which one comes to a greater maturity; the other, in fact,
remaining at a very early stage of development. The more
complete dentition belongs to the milk series, as is the case with
the Toothed Whales. A very interesting conclusion with regard
to the derivation of the simple conical teeth of Whales seems to
follow from the development of these structures in JBalaenopterd.
There are in the young foetus fewer teeth than in the more
advanced embryo. Now in the younger embryo some of the
teeth are furnished with more than one cusp; they are bi- or
even tri-coaodont. As Sir H. Owen, observed, the teeth—some of
* Tlieae have been recorded by Professor Howes in ike Porpoise.